The human spine includes thirty-three vertebrae. The vertebrae interlock with one another to form a spinal column. Each vertebra has a cylindrical bony body (vertebral body), two pedicles extending from the vertebral body, a lamina extending from the pedicles, two wing-like projections extending from the pedicles, a spinous process extending from the lamina, a pars interarticularis, two superior facets extending from the pedicles, and two inferior facets extending from the lamina. The vertebrae are separated and cushioned by thin pads of tough, resilient fiber known as intervertebral discs. Intervertebral discs provide flexibility to the spine and act as shock absorbers during activity. A small opening (foramen) located between each vertebra allows passage of nerves. When the vertebrae are properly aligned, the nerves pass through without a problem. However, when the vertebrae are misaligned or a constriction is formed in the spinal canal, the nerves get compressed and may cause back pain, leg pain, or other neurological disorders.
Disease, the effects of aging, or physical trauma resulting in damage to the spine has been treated in many instances by fixation or stabilization of the effected vertebra. A wide variety of spinal fixation apparatuses have been employed in surgical procedures for correcting spinal injuries and the effects of spinal diseases.
Disorders of the spine that may cause misalignment of the vertebrae or constriction of the spinal canal include spinal injuries, infections, tumor formation, herniation of the intervertebral discs (i.e., slippage or protrusion), arthritic disorders, and scoliosis. In these pathologic circumstances, surgery may be tried to either decompress the neural elements and/or fuse adjacent vertebral segments. Decompression may involve laminectomy, discectomy, or corpectomy. Laminectomy involves the removal of part of the lamina, i.e., the bony roof of the spinal canal. Discectomy involves removal of the intervertebral discs. Corpectomy involves removal of the vertebral body as well as the adjacent intervertebral discs.
The time-honored method of addressing the issues of neural irritation and instability resulting from severe disc damage has largely focused on removal of the damaged disc and fusing the adjacent vertebral elements together. Removal of the disc relieves the mechanical and chemical irritation of neural elements, while osseous union (bone knitting) solves the problem of instability.
After a partial or complete discectomy, the normally occupied space between adjacent vertebral bodies is subject to collapse and/or misalignment due to the absence of all or a part of the intervertebral disc. In such situations, the physician may insert one or more prosthetic spacers between the affected vertebrae to maintain normal disc spacing and/or the normal amount of lordosis in the affected region.
Typically, a prosthetic implant is inserted between the adjacent vertebrae and may include pathways that permit bone growth between the adjacent vertebrae until they are fused together. As is typical, the intervertebral spaces are accessed either anteriorly or posteriorly. It would be desirable to access the intervertebral spaces via an approach that provides greater access to the surgical area while applying the least amount of stress to the surrounding tissue.
Additionally, one of the challenges during surgery is to ensure that the vertebral bodies can maintain parallel distraction so as not to move the spine out of alignment.
Therefore, a need exists for systems and/or devices used in spinal surgery that provides greater access and visualization of a surgical area while applying the least amount of stress to the surrounding tissue and/or maintains alignment and spacing of the vertebral bodies and rigid attachment to the vertebral bodies.